45mm-wide twin-axis servodrive is ‘world’s thinnest’

02 December, 2016

The German motion engineer Stober has developed what it claims is the world’s narrowest multi-axis servodrive. The modular, rack-based SI6 system includes double-axis modules (2 x 5A) that are 45mm wide, resulting in six-axis systems that are 18cm wide, and 20-axis systems that are less than 50cm wide, including power supplies. The drives have a position, speed and current cycle time of 62.5µs.

The modules are linked to a central power supply via a patented backplane containing a common DC bus based on 12 x 5mm copper conductor rails that can carry up to 200A. Individual axes do not need their own fuses or cabling. The modules click into position, without needing special tools. Energy generated by one drive when braking can be used to accelerate another, thus saving energy and allowing smaller power supplies to be used.

There are two power supplies available: a 10kW, 25A version that is 45mm wide; and a 20kW, 50A version that is 65mm wide. The power supplies can operate with a single central resistor for emergency stops. Redundant supplies are not needed, and up to three power supplies can be used in parallel.

If one axis in a twin-axis drive is not being used at its full nominal current, the second axis can be used at a higher current than nominal. So, for example, if one axis in a 2 x 5A drive needs 3A, the second axis can draw 6A, possibly allowing a smaller drive to be specified.

As well as the 45mm-wide 5A modules, the drives are also available in 65mm-wide modules that include single axes rated at 12A or 22A, and double axes rated at 2 x 12A. The modules can also be combined with drives from Stober’s SD6 series, allowing precise numbers of axes to be configured.

The drives can accelerate a Stober EZ401 synchronous servomotor up to 3,000 rpm in 10ms. They process encoder information up to 64 bits and calculate it without rounding errors (using floating-point arithmetic). More than 33 million encoder positions can be resolved per revolution, even though current encoder systems deliver only 37 bits.

A single-cable connection, including power, can be used with encoder communications via Hiperface DSL. When using Hiperface DSL or EnDat 2.2, data from Stober’s EZ servomotors can be parameterised using electronic nameplates. Other types of feedback supported include resolver, SSI and incremental (TTL or HTL).

The servodrives can communicate via Ethernet-based fieldbus systems such as EtherCat and Profinet. They support the Ethernet-over-EtherCat protocol (EoE), allowing Ethernet data to be transported via an EtherCat system. Using the CiA 402 device profile, the servodrives can be integrated into controller- or drives-based systems.

A built-in Safe Torque-Off function can be controlled via the drive terminals or via Fail Safe over EtherCat (FSoE). The drives comply with Performance Level e (Cat 4) in accordance with EN 13849-1.